The present invention relates to a screening assembly that is designed to be simple and versatile being relatively inexpensive to construct and maintain, and having a minimum number of component parts to perform the necessary operations. Prior art screening assemblies have been effective in performing their ultimate function, however they often are too bulky for many types of uses and environments and can be unnecessarily complicated.
The simplicity and versatility of the present invention are readily apparent when the small number of component parts thereof are considered, and when it is considered the assembly according to the invention may be used in many situations and environments. The screening assembly according to the present invention is capable of separating out knots, fiber bundles, shives and scrap material from suspensions of cellulosic fiber material having consistencies on the order of 8 to 10%, and can accomplish this without any air introduction so that no foam is developed, and can accomplish this without interruptions due to clogging of the screening element.
According to the present invention a screening assembly is provided comprising a closed housing having an inlet, a first outlet, and a second outlet. While the terms "inlet" and "outlet" are used in the present specification and claims for convenience, it should not be assumed that the recited elements can be used only as inlets or outlets, or always function as such. The screening assembly according to the invention further comprises a screen drum mounted for rotation about an axis and having a plurality of circumferential through-extending slots formed along the exterior periphery thereof, and disposed in planes substantially perpendicular to the axis of rotation.
Means are provided for rotating the drum about its axis of rotation, and means are provided for mounting the drum for rotation about its axis within the housing so that suspension passing from the inlet to the second outlet must pass through the drum slots, the second outlet being essentially coaxial with the drum, and so that suspension flows pass the drum from the inlet to the first outlet. Means are also provided for preventing short-circuiting of suspension flow from the inlet to the first outlet, and for dislodging suspension particles caught within the drum slots. Such short-circuiting preventing and particle dislodging means may comprise a single component, such as a barrier member mounted on a short housing segment between the inlet and first outlet, and having a plurality of comb-like teeth extending into the drum circumferential slot. The barrier member preferably has concave surfaces formed on portions thereof adjacent the inlet and first outlet to facilitate directing the suspension.
The inlet and the first outlet preferably lie in a common plane, each having a center line, and the housing preferably connects the inlet and the first outlet so that the center lines thereof make an angle of about 45.degree.-90.degree. with respect to each other. The second outlet preferably is disposed perpendicular to the common plane containing the inlet and the first outlet.
The drum preferably has a plurality of axially extending surface manifestations formed thereon to facilitate transportation of the suspension being screened by the drum. Such surface manifestations may comprise of a plurality of circumferentially spaced grooves, or a plurality of circumferentially spaced raised portions.
In addition to the barrier member, accessory cleaning devices may be provided spaced from the barrier member around the circumference of the drum, and having a plurality of comb-like teeth extending into the drum slots to effect dislodgement of suspension particles therefrom. Such a cleaning device or devices are mounted and dimensioned to allow passage of suspension therepast from the inlet to the first outlet.
It is the primary object of the present invention to provide a simple, versatile, and effective screening assembly. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.